Question: You said "since I started riding...", but how long have you been riding?

I had knee pain in my right knee similar to your pain, just under the knee-cap. Pedalling was actually fine. Climbing the stairs hurt but only as I raised my leg to place it on the next step. Just the action of extending my leg caused it to hurt. Then after a couple weeks it got better and the pain started on my left knee just as the right was getting better. Then I had noticed when I removed my pedals and put them back on (switched to/from other bike for rollers), that both axles were wobbling as I threaded them back on. I'm guessing the axles were bent. So I decided to replace my pedals. I was planning to do so anyways. I got the Crank Brothers EggBeaters to replace the cheapo OEM single-sided SPD pedals that came with my Felt. After a couple rides my left knee was feeling better and my right knee pain was gone all together. Now both kness are totally without pain. So there's probably something in you fit or equipment that's causing this pain. Have you changed anything like seat height/position prior to your knee pain? Or maybe it just was an accumulation of a long time with some misalignment.

I should've seen a Dr. but I didn't and I got lucky with my "fix". If the knee pain would've remained, then I would've seen a Dr. Looking back, it probably was not the smart move as I could've damaged my knees even worse. Ultimately, the choice is yours whether you wan to see the Dr. or try to remedy it yourself.
Just remember that you have to live with that decision.